The Properties>Materials>drop-down list won’t allow a material change for an object exploded from a linked block.
It shows me the current material “Custom (10)” with (as one would expect) all its settings locked. However, choosing a new custom or existing material from the drop-down menu has no effect; the choice returns to “Custom (10).” Below the drop-down a yellow panel says: “some items in the drop-down list may be hidden by the main Material Editor’s search facility. Click to go to the search”
Clicking “to go to the search” gives me a list of iterations of materials named “Custom (n)” - I can create a new material there (it disappears from the list if I change the name from “Custom”, though) but again changing the setting has no effect - the field reverts to the original material after any other choice.